The present invention relates to a clutch comprising a driving rotor and a driven rotor, and more particularly, to a clutch for blocking the transmission of rotation from a driven rotor to a driving rotor and a driving apparatus equipped with the clutch.
A general power window apparatus comprises a driving apparatus serving as a driving source, and a driven device driven by the driving apparatus which moves a windowpane up and down, specifically, a lifting mechanism. The driving apparatus includes an output unit equipped with a gear mechanism. The rotation of the motor is transmitted to the lifting mechanism through the gear mechanism. The lifting mechanism converts the rotation of the motor to up/down movements of the windowpane.
When external force is applied to the windowpane while the motor is not driven, the external force is transmitted from the windowpane to the motor through the lifting mechanism and the gear mechanism. Therefore, when external force is applied to the windowpane, the windowpane is allowed to move. Further, the gear constituting the gear mechanism may be damaged.
To prevent the movement of the windowpane caused by external force, the driving apparatus is equipped with a clutch. The clutch is located in the middle of a power transmission path between the motor and the lifting mechanism in the output unit. The clutch allows the power of the motor to be transmitted to the lifting mechanism through the output unit. However, when external force is applied to the windowpane, the clutch is locked to make a rotation impossible in order to prevent the external force from moving the lifting mechanism. In other words, the clutch blocks the transmission of movement from the lift mechanism to the motor.
Japanese Unexamined Patent Publication No. Hei 7-103260 discloses a clutch of this type. As illustrated in FIG. 52, the clutch 750 comprises a cylindrical clutch housing 751, a driving rotor 762, a driven rotor 753, and a plurality of rolling bodies 754. The driving rotor 762 is rotated by a driving source (not shown) such as a motor. The driving rotor 762 has a plurality of engagement bodies 752 arranged at equal angular intervals which are rotatably accommodated in a clutch housing 751. The driven rotor 753 is accommodated in the clutch housing 751 such that it is surrounded by the engagement bodies 752. The driven rotor 753 is provided with a plurality of restriction faces 753a on its outer peripheral face. The rolling bodies 754 are located between the restriction faces 753a and the inner peripheral face of the clutch housing 751 such that they are positioned between respective two adjacent engagement bodies 752.
As the driving rotor 762 is rotated by the driving source, ends 752a of the engagement bodies 752 are engaged with the corresponding rolling bodies 754. With further rotation of the driving rotor 762, the rolling bodies 754 are held between the engagement bodies 752 and the restriction faces 753a of the driven rotor 753 to couple the driven rotor 753 to the driving rotor 762 for rotation integral therewith. Thus, the rotation of the driving rotor 762 is transmitted to the driven rotor 753 through the rolling bodies 754, causing the driven rotor 753 to rotate together with the driving rotor 762 in the clutch housing 751. With the rotation of the driven rotor 753, a driven device (not shown) coupled to the driven rotor 753 is driven.
On the other hand, as the driven rotor 753 is rotated by a movement of the driven device resulting from external force or the like, the restriction faces 753a moves the rolling bodies 754 toward the inner peripheral face of the clutch housing 751 through the respective two adjacent engagement bodies 752. With further rotation of the driven rotor 753, the rolling bodies 754 are held between the restriction faces 753a and the inner peripheral face of the clutch housing 751 to lock the driven rotor 753 to the clutch housing 751 to prevent the rotation thereof. Thus, the transmission of rotation from the driven rotor 753 to the driving rotor 762 is blocked, together with the movement of the driven device being blocked.
In the foregoing clutch 750, when the rolling bodies 754 are held between the restriction faces 753a and the engagement bodies 752 by the rotation of the driving rotor 762, the rolling bodies 754 may not be released from the held state when the driven rotor 753 is rotated subsequently by a movement of the driven device. In such a case, the driven rotor 753 is not locked in a manner disabling the rotation, thereby allowing the rotation of the driven rotor 753 to be transmitted to the driving rotor 762 through the rolling bodies 754, thereby failing to block the movement of the driven device.
Japanese Unexamined Patent Publication No. Hei 8-200401, on the other hand, discloses a clutch for transmitting the rotation of a driving rotor to a driven rotor through a knock pin (switch pin). However, the knock pin is in contact with a member engaged with the knock pin with a small area. For this reason, during the transmission of rotation, force intensively acts between the knock pin and the member engaged with the knock pin. For making the clutch durable to such intensive force, the clutch must be formed with a high strength. This increases a manufacturing cost of the clutch.
It is an object of the present invention to provide a clutch that is capable of reliably blocking the transmission of rotation from a driven rotor to a driving rotor and of reducing a required strength, and a driving apparatus equipped with the clutch.
To achieve the above object, a clutch according to the present invention comprises a driving rotor coupled to a driving source, a driven rotor directly engaged with the driving rotor such that the driven rotor is driven by the driving rotor, a housing for accommodating the driving rotor and the driven rotor, and a lock member located between the driven rotor and the housing. The lock member is circulated about an axial center of the driving rotor associated with rotation of the driving rotor. The lock member is held between the driven rotor and the housing to block rotation of the driven rotor relative to the housing when the driven rotor itself is rotated. The lock member is released from the held state to allow the driving rotor to rotate the driven rotor relative to the housing when the driving source rotates the driving rotor.
The rotation of the driven rotor itself relative to the housing is blocked by the lock member which is held between the driven rotor and the housing. When the driving source rotates the driving rotor, the lock member is released from the held state. This allows the transmission of the rotation from the driving rotor to the driven rotor without fail and blocks the transmission of the rotation from the driven rotor to the driving rotor without fail, as compared with a clutch in which a lock member is brought into a held state whenever the driving rotor is rotated or the driven rotor is rotated. Further, since the driven rotor is directly engaged with the driving rotor, a large contact area can be ensured between both rotors. For this reason, the strength required for both rotors can be reduced.
The present invention also provides a driving apparatus comprising a clutch constructed as described above. The driving apparatus comprises a motor having a rotating shaft and functioning as a driving source, and an output unit coupled to the motor. The output unit comprises a decelerating mechanism for decelerating the rotation of the rotating shaft before transmission to a driven device. The clutch is located between the rotating shaft and the decelerating mechanism.
The clutch located between the rotating shaft and the decelerating mechanism is not subjected to a large load. Therefore, the durability required for the clutch can be reduced with a result of a smaller-size clutch.
In another aspect of the driving apparatus according to the present invention, the clutch is located between the decelerating mechanism and the driven device in the output unit. In this way, a movement of the driven device based on force applied to the driven device can be satisfactorily blocked in a stage near the driven device.